Pull VFIO updates from Alex Williamson:

 - Replace global vfio-pci lock with per bus lock to allow concurrent
   open and release (Alex Williamson)

 - Declare mdev function as static (Paolo Cretaro)

 - Convert char to u8 in mdev/mtty sample driver (Nathan Chancellor)

* tag 'vfio-v4.21-rc1' of git://github.com/awilliam/linux-vfio:
  vfio-mdev/samples: Use u8 instead of char for handle functions
  vfio/mdev: add static modifier to add_mdev_supported_type
  vfio/pci: Parallelize device open and release